Clinical Pharmacology Perspective on Development of Adeno-Associated Virus Vector-Based Retina Gene Therapy.

Adeno-associated virus (AAV) vector-based gene therapy is an innovative modality being increasingly investigated to treat diseases by modifying or replacing defective genes or expressing therapeutic entities. With its unique anatomic and physiological characteristics, the eye constitutes a very attractive target for gene therapy. Specifically, the ocular space is easily accessible and is generally considered "immune-privileged" with a low risk of systemic side effects following local drug administration. As retina cells have limited cellular turnover, a one-time gene delivery has the potential to provide long-term transgene expression. Despite the initial success with voretigene neparvovec (Luxturna), the first approved retina gene therapy, there are still challenges to be overcome for successful clinical development of these products and scientific questions to be answered. The current review paper aims to integrate published experience learned thus far for AAV-based retina gene therapy related to preclinical to clinical translation; first-in-human dose selection; relevant bioanalytical assays and strategies; clinical development considerations including trial design, biodistribution and vector shedding, immunogenicity, transgene expression, and pediatric populations; opportunities for model-informed drug development; and regulatory perspectives. The information presented herein is intended to serve as a guide to inform the clinical development strategy for retina gene therapy with a focus on clinical pharmacology.

Population Dose-Response-Time Analysis of Itch Reduction and Patient-Reported Tolerability Supports Phase III Dose Selection for Linerixibat.

Increase in serum bile acids (BAs) in patients with primary biliary cholangitis (PBC) may play a causal role in cholestatic pruritus (itch). Linerixibat is a selective small molecule inhibitor of the ileal bile acid transporter, which blocks re-absorption of BAs in the gastrointestinal tract thereby lowering BAs in the systemic circulation and reducing itch. One consequence is excess BAs in the colon, leading to diarrhea and abdominal pain. GLIMMER (NCT02966834) was a placebo-controlled phase IIb dose-ranging trial of linerixibat once (q.d.) or twice daily (b.i.d.) in adults with moderate to severe pruritus and PBC. To determine the optimal dose for maximum itch reduction while minimizing diarrhea, a kinetic-pharmacodynamic (k-PD) model was developed using data from GLIMMER. The PD end point modeled was worst daily itch, derived from itch score reported by patients b.i.d. A proportional odds model was developed post hoc to indicate the probability of diarrhea occurrence, a patient-reported outcome (GI-5) recorded weekly. The final k-PD model successfully described the effects of linerixibat and placebo on itch. Model simulations were consistent with the observed dose-dependent increase in the average number of itch responders (patients with a ≥ 2-point improvement in itch). This was paralleled by a dose-dependent increase in the probability of higher diarrhea frequency scores. The b.i.d. dosing regimens led to a modest increase in the number of itch responders as compared with q.d. dosing. This quantitative framework highlights the trade-off between benefit and tolerability and supported the selection of 40 mg b.i.d. in the phase III GLISTEN trial (NCT04950127).

Machine learning-guided covariate selection for time-to-event models developed from a small sample of real-world patients receiving bevacizumab treatment.

Therapeutic outcomes in patients with metastatic colorectal cancer (mCRC) receiving bevacizumab treatment are highly variable, and a reliable predictive factor is not available. Progression-free survival (PFS) and overall survival (OS) were recorded from an observational, prospective study after 5 years of follow-up, including 46 patients with mCRC receiving bevacizumab treatment. Three vascular endothelial growth factor (VEGF)-A and two intercellular adhesion molecule-1 genes polymorphisms, age, gender, weight, dosing scheme, and co-treatments were collected. Given the relatively small number of events (37 [80%] for the PFS and 26 [57%] for the OS), to study the effect of these covariates on PFS and OS, a covariate analysis was performed using statistical and supervised machine learning techniques, including Cox regression, penalized Cox regression techniques (least absolute shrinkage and selection operator [LASSO], ridge regression, and elastic net), survival trees, and survival forest. The predictive performance of each method was evaluated in bootstrapped samples, using prediction error curves and the area under the curve of the receiver operating characteristic. The LASSO penalized Cox-regression model showed the best overall performance. Nonlinear mixed effects (NLME) models were developed, and a conventional stepwise covariate search was performed. Then, covariates identified as important by the LASSO model were included in the base NLME models developed for PFS and OS, resulting in improved models as compared to those obtained with the stepwise covariate search. It was shown that having gene polymorphisms in VEGFA (rs699947 and rs1570360) and ICAM1 (rs1799969) are associated with a favorable clinical outcome in patients with mCRC receiving bevacizumab treatment.

Knowledge dissemination and central indexing of resources in pharmacometrics: an ISOP education working group initiative.

Pharmacometrics is a constantly evolving field that plays a major role in decision making in drug development and clinical monitoring. Scientists in Pharmacometrics, especially in their early phases of career, are often faced with the challenge of identifying adequate resources for self-training and education. Hence, the ISoP Education Committee through its working group dedicated to Central Indexing and knowledge Dissemination has built a database of worldwide educational programs and most common references in Pharmacometrics.

External Evaluation of Risperidone Population Pharmacokinetic Models Using Opportunistic Pediatric Data.

Risperidone is approved to treat schizophrenia in adolescents and autistic disorder and bipolar mania in children and adolescents. It is also used off-label in younger children for various psychiatric disorders. Several population pharmacokinetic models of risperidone and 9-OH-risperidone have been published. The objectives of this study were to assess whether opportunistically collected pediatric data can be used to evaluate risperidone population pharmacokinetic models externally and to identify a robust model for precision dosing in children. A total of 103 concentrations of risperidone and 112 concentrations of 9-OH-risperidone, collected from 62 pediatric patients (0.16-16.8 years of age), were used in the present study. The predictive performance of five published population pharmacokinetic models (four joint parent-metabolite models and one parent only) was assessed for accuracy and precision of the predictions using statistical criteria, goodness of fit plots, prediction-corrected visual predictive checks (pcVPCs), and normalized prediction distribution errors (NPDEs). The tested models produced similarly precise predictions (Root Mean Square Error [RMSE]) ranging from 0.021 to 0.027 nmol/ml for risperidone and 0.053-0.065 nmol/ml for 9-OH-risperidone). However, one of the models (a one-compartment mixture model with clearance estimated for three subpopulations) developed with a rich dataset presented fewer biases (Mean Percent Error [MPE, %] of 1.0% vs. 101.4, 146.9, 260.4, and 292.4%) for risperidone. In contrast, a model developed with fewer data and a more similar population to the one used for the external evaluation presented fewer biases for 9-OH-risperidone (MPE: 17% vs. 69.9, 47.8, and 82.9%). None of the models evaluated seemed to be generalizable to the population used in this analysis. All the models had a modest predictive performance, potentially suggesting that sources of inter-individual variability were not entirely captured and that opportunistic data from a highly heterogeneous population are likely not the most appropriate data to evaluate risperidone models externally.

Consensus Statement Regarding the Efficacy and Safety of Long-Term Low-Dose Colchicine in Gout and Cardiovascular Disease.

Over the last decade, evidence has demonstrated that long-term, low-dose colchicine (0.5 mg daily) is effective for preventing gout flare and cardiovascular (CV) events in a wide range of patients. Given the potentially expanding use of colchicine in CV disease, we here review and update the biologic effects and safety of colchicine based on recent data gathered from bench and pharmacodynamic studies, clinical reports, controlled clinical trials, and meta-analyses, integrated with important studies over the last 50 years, to offer a consensus perspective by experts from multiple specialties familiar with colchicine's long-term use. We conclude that the clinical benefits of colchicine in gout and CV disease achieved at low dose do not sustain serum levels above the upper limit of safety when used in patients without advanced renal or liver disease or when used concomitantly with most medications. Further, data accrued over the last 50 years strongly suggest that the biologic effects of long-term colchicine do not increase the risk of cancer, sepsis, cytopenia, or myotoxicity.

Physiologically-based pharmacokinetic modeling of oxcarbazepine and levetiracetam during adjunctive antiepileptic therapy in children and adolescents.

Oxcarbazepine (OXZ) and levetiracetam (LEV) are two new generation anti-epileptic drugs, often co-administered in children with enzyme-inducing antiepileptic drugs (EIAEDs). The anti-epileptic effect of OXZ and LEV are linked to the exposure of OXZ's active metabolite 10-monohydroxy derivative (MHD) and (the parent) LEV, respectively. However, little is known about the confounding effect of age and EIAEDs on the pharmacokinetics (PKs) of MHD and LEV. To address this knowledge gap, physiologically-based pharmacokinetic (PBPK) modeling was performed in the PK-Sim software using literature data from children greater than or equal to 2 years of age. Age-related changes in clearance (CL) of MHD and LEV were characterized, both in the presence (group 1) and absence (group 2) of concomitant EIAEDs. The drug-drug interaction effect of EIAEDs was estimated as the difference in CL estimates between groups 1 and 2. PBPK modeling suggests that bodyweight normalized CL (ml/min/kg) is higher in younger children than their older counterparts (i.e., due to an influence of age). Concomitant EIAEDs further increase MHD's CL to a fixed extent of 25% at any age, but EIAEDs' effect on LEV's CL increases with age from 20% (at 2 years) to 30% (at adolescence). Simulations with the maximum recommended doses (MRDs) revealed that children between 2 and 4 years and greater than 4 years, who are not on EIAEDs, are at risk of exceeding the reference exposure range for OXZ and LEV, respectively. This analysis demonstrates the use of PBPK modeling in understanding the confounding effect of age and comedications on PKs in children and adolescents.

Colchicine for the treatment of COVID-19 patients: efficacy, safety, and model informed dosage regimens.

Colchicine is widely investigated for cardioprotection of COVID-19 patients since it can prevent the phenomenon of 'cytokine storm' and may reduce the complications arising from COVID-19. Despite the potentially beneficial effects of colchicine, there is no consensus on the appropriate dosage regimen and numerous schemes are currently used.In this study, simulations were performed to identify the ability of dosage regimens to attain plasma levels in CVOID-19 patients, known to be generally safe and efficacious. Since renal and hepatic impairment, as well as, drug-drug interactions have been identified to be the most significant factors increasing colchicine toxicity, the impact of these interactions was assessed in the simulations.Some dosage regimens lead to high colchicine concentrations, while others result in sub-therapeutic levels. Additional dosage schemes were proposed in this study aiming to be applied in patients with clearance insufficiency. Colchicine administration of 0.5 mg twice daily, can be considered safe and effective. In cases of clearance impairment, doses as low as 0.25 mg thrice or twice daily should be applied.Colchicine is a narrow therapeutic index drug and dosage regimens tailored to patients' needs should be designed.

Investigating the Impact of Gastric Emptying on Pharmacokinetic Parameters Using Delay Differential Equations and Principal Component Analysis.

BACKGROUND AND OBJECTIVES: Losartan presents multiple peaks after single oral administration, which can be attributed to gastric emptying. The aim of this study was to describe the multiple peak phenomenon of losartan using a delay differential model and a model with sine function. The impact of gastric emptying on pharmacokinetic parameters was investigated by applying principal component analysis to the individual parameter estimates. METHODS: Using MonolixTM, two population pharmacokinetic models were developed to describe the multiple peak phenomenon; the first using delay differential equations and the second using a sine function. Matlab® delay differential equation solver was used to arithmetically solve both functions. Principal component analysis and all statistical analyses were performed in the R language. RESULTS: The description of losartan multiple peaks can be achieved by the use of either delay differential equations or typical sine wave functions. Principal component analysis unveiled the impact of gastric emptying on the pharmacokinetic parameters. In the case of the delay differential equation model, a negative relationship was found between the constant delay tau1 and the parameters reflecting rate and extent of absorption (i.e., area under the curve [AUC], peak plasma concentration [Cmax], and the absorption rate constant). Similar results were obtained from the sine model, where a higher amplitude and lower period (i.e., higher frequency) of gastric emptying were associated with higher AUC and Cmax values. CONCLUSIONS: The observed multiple peaks for certain drugs like losartan can be attributed to gastric emptying. Parameters describing gastric emptying can be associated with pharmacokinetic metrics like AUC and Cmax.

Optimization of hydroxychloroquine dosing scheme based on COVID-19 patients' characteristics: a review of the literature and simulations.

During the recent COVID-19 outbreak hydroxychloroquine (HCQ) has been proposed as a safe and effective therapeutic option. However, a wide variety of dosing schemes has been applied in the clinical practice and tested in clinical studies. An extended literature survey was performed investigating the pharmacokinetics, the efficacy and safety of HCQ in COVID-19 treatment. Population pharmacokinetic models were retrieved from the literature and after evaluation and assessment one was selected in order to perform simulations. The most commonly applied dosing schemes were explored for patients with different weights and different levels of HCQ clearance impairment. Model-based simulations of HCQ concentrations revealed that high initial doses followed by low and sparse doses may offer significant benefits to patients by decreasing the viral load without reaching levels considered to produce adverse effects. For instance, the dosing scheme proposed for a 70 kg adult with moderate COVID-19 symptoms would be 600 mg upon diagnosis, 400 mg after 12 h, 300 mg after 24 h, 200 mg after 36 h, followed by 200 mg BID for 4 d, followed by 200 mg OD for 5 d. Based on the results from simulations performed and the currently published knowledge regarding HCQ in COVID-19 treatment, this study provides evidence that a high loading dose followed by sparse doses could offer significant benefits to the patients.

Delay differential equations for the description of Irbesartan pharmacokinetics: A population approach to model absorption complexities leading to dual peaks.

Irbesartan is a poorly soluble BCS class II compound with weak acidic properties. After oral administration, dual peaks are noted in its concentration (C) - time (t) profile, a phenomenon that may be attributed to enterohepatic recirculation, gastric emptying and/or other absorption complexities related to its pH- and buffer capacity-dependent dissolution behavior. A population pharmacokinetic model, encompassing delay differential equations, was found the most appropriate approach to describe dual peaks in irbesartan's C-t profiles. Parameters estimated were: the absorption rate constant in the central compartment (ka = 0.304 h-1), the constant time delay between the administration and the absorption (T=1.68 h), the apparent volume of distribution of the central (V1/F = 13.8 L) and peripheral (V2/F = 85.8 L) compartment, the apparent clearance from the central compartment (CL/F = 13.5 L/h), and the inter-compartmental clearance (Q/F = 17.7 L/h). Using simulations, it was made evident that changing the time delay results in significant changes of peak plasma concentrations but not of its blood pressure-lowering effect. In conclusion, delay differential equations may be useful to model dual peaks arising from absorption complexities, while changes of the time delay that reflect physiological processes that take place before absorption may have significant implications in proving bioequivalence.

Chloroquine dosage regimens in patients with COVID-19: Safety risks and optimization using simulations.

Currently no specific medicinal treatment exists against the new SARS-CoV2 and chloroquine is widely used, since it can decrease the length of hospital stay and improve the evolution of the associated COVID-19 pneumonia. However, several safety concerns have been raised from chloroquine use due to the lack of essential information regarding its dosing. The aim of this study is to provide a critical appraisal of the safety information regarding chloroquine treatment and to apply simulation techniques to unveil relationships between the observed serious adverse events and overdosing, as well as to propose optimized dosage regimens. The dose related adverse events of chloroquine are unveiled and maximum tolerated doses and concentration levels are quoted. Among others, treatment with chloroquine can lead to severe adverse effects like prolongation of the QT interval and cardiomyopathy. In case of chloroquine overdosing, conditions similar to those produced by SARS-CoV2, such as pulmonary oedema with respiratory insufficiency and circulatory collapse, can be observed. Co-administration of chloroquine with other drugs for the treatment of COVID-19 patients, like azithromycin, can further increase the risk of QT prolongation and cardiomyopathy. For elder patients there is a high risk for toxicity and dose reduction should be made. This study unveils the risks of some widely used dosing regimens and binds the observed serious adverse events with dosing. Based on simulations, safer alternative dosage regimens are proposed and recommendations regarding chloroquine dosing are made.

Pharmacogenetics in Model-Based Optimization of Bevacizumab Therapy for Metastatic Colorectal Cancer.

Vascular endothelial growth factor A (VEGF-A) and intercellular adhesion molecule 1 (ICAM-1) are significant regulators of angiogenesis, an important biological process involved in carcinogenesis. Bevacizumab, an anti-VEGF monoclonal antibody (MAB), is approved for the treatment of metastatic Colorectal cancer (mCRC), however clinical outcomes are highly variable. In the present study, we developed a pharmacokinetic (PK), a simplified quasi-steady state (QSS) and a pharmacokinetic/pharmacodynamic (PK/PD) model to identify potential sources of variability. A total of 46 mCRC patients, who received bevacizumab in combination with chemotherapy were studied. VEGF-A (rs2010963, rs1570360, rs699947) and ICAM-1 (rs5498, rs1799969) genes' polymorphisms, age, gender, weight, and dosing scheme were investigated as possible co-variates of the model's parameters. Polymorphisms, trough, and peak levels of bevacizumab, and free VEGF-A were determined in whole blood and serum. Data were analyzed using nonlinear mixed-effects modeling. The two-compartment PK model showed that clearance (CL) was significantly lower in patients with mutant ICAM-1 rs1799969 (p < 0.0001), inter-compartmental clearance (Q) was significantly higher with mutant VEGF-A rs1570360 (p < 0.0001), and lower in patients with mutant VEGF-A rs699947 (p < 0.0001). The binding QSS model also showed that mutant ICAM-1 rs1799969 was associated with a lower CL (p = 0.0177). Mutant VEGF-A rs699947 was associated with a lower free VEGF-A levels, prior to the next dose (p = 0.000445). The above results were confirmed by the PK/PD model. Findings of the present study indicated that variants of the genes regulating angiogenesis might affect PK and PD characteristics of bevacizumab, possibly influencing the clinical outcomes.

Pharmacokinetic and pharmacodynamic modeling of levetiracetam: investigation of factors affecting the clinical outcome.

This study aimed to evaluate the pharmacokinetics and pharmacodynamics of oral levetiracetam therapy in drug refractory adult epileptic outpatients, as well as factors affecting them. Concentration-time data were collected at steady state, while seizure recurrence was monitored for 13 months. Non-linear mixed effects modeling was applied, and covariates assessed included weight, height, age, daily dose and creatinine clearance.Plasma concentrations of levetiracetam were best described by a one-compartment pharmacokinetic model (V/F = 34.7 L) with first-order absorption (ka = 0.616 h-1) and clearance (CL/F = 3.26 L/h). Patient's CrCL was found to significantly affect levetiracetam clearance (beta = 0.795). Time to seizure occurrence followed an exponential distribution and the mean time to seizure occurrence was estimated Te = 22.08 days. Seizure rate per month followed a Poisson distribution, while mean seizure rate per month was estimated λ = 1.33. Daily dose significantly affected the mean estimated time to seizure (beta = -2.2) and the mean monthly seizure rate (beta = 2.27) in a reverse way. Using discrete time Markov chains, it was shown that the transition probability from focal seizures to focal to bilateral tonic-clonic is significantly altered in relation to patient's CrCL.Simulations showed that dose should be adjusted in relation to CrCL, while low doses of levetiracetam are more effective for seizure control. Modeling and simulation in every-day clinical practice may provide significant information for the optimization of seizure control using well-known agents.

Modelling gastric emptying: A pharmacokinetic model simultaneously describing distribution of losartan and its active metabolite EXP-3174.

Losartan presents multiple peaks in the concentration-time profile. This characteristic can be attributed to gastric emptying, which is known to significantly affect the disposition of highly soluble and permeable compounds. The aim of this study was to develop a population pharmacokinetic model for losartan and its active metabolite (EXP-3174) in order to describe the effect of gastric emptying on their disposition. Population pharmacokinetic analysis was performed using concentration-time data derived from a crossover bioequivalence study in 31 volunteers after a single oral dose of 100 mg losartan potassium in the fasted state. Delay differential equations (DDEs) were explored for the description of losartan absorption and EXP-3174 formation, since when solved they result in oscillatory behaviour. A two-compartment model preceded by a pre-absorption compartment (referring to small intestine) adequately described the observed concentration-time profiles of losartan. In the final model, a sinusoidal equation was used for the description of gastric emptying in view of its simplicity, leading to enhanced stability of the model and its capacity to describe periodicity. In case of EXP-3174, a one-compartment model, with a delayed first-order formation rate from losartan's central compartment, best described its disposition. Using the model developed, it was shown through simulations that changes in gastric emptying parameters lead to changes in the C-t profiles of both compounds. In particular, plasma oscillations can be enhanced or completely suppressed, simply by changing parameters affecting gastric emptying.

Ex vivo evaluation of degradation rates of metronidazole and olsalazine in distal ileum and in cecum: The impact of prandial state.

PURPOSE: Evaluate ex vivo the bacterial metabolism induced degradation rates of mesalamine (negative control), metronidazole and olsalazine in distal ileum and in cecum. METHODS: The contents of distal ileum and cecum were collected during colonoscopy under anaerobic conditions from twelve healthy adults in the fasted and in the fed state. To eliminate potential effects of enzymes that may exist in the fluid of lower intestine, each sample was ultracentrifuged and the precipitate was diluted with a volume of normal saline equivalent to that of the supernatant, after ultracentrifugation of intestinal contents from which the specific precipitate had been obtained. Degradation of the three model drugs in individual materials was evaluated anaerobically. RESULTS: Mesalamine was stable in all cases. Degradation rates of metronidazole and olsalazine were higher in cecum than in distal ileum, only in the fasted state; no trend could be observed in the fed state. Degradation rates of metronidazole and olsalazine were decreased in the fed state in the cecum; no trend could be observed in distal ileum. CONCLUSIONS: In the fasted state, bacterial activity is higher in cecum than in distal ileum. Food residues decrease bacterial metabolism degradation rates of drugs in cecum.

The Impact of Handling and Storage of Human Fecal Material on Bacterial Activity.

Fecal material prepared from human stools is frequently used for the assessment of bacterial degradation of active pharmaceutical ingredients as relevant data are useful for evaluating the potential for colonic drug delivery. The impact of handling and storage of human fecal material on bacterial activity was assessed by evaluating the degradation characteristics of metronidazole and olsalazine. Multiple freeze (-70°C)-thaw cycles should be avoided. Incubation of frozen material for about 2 h in the anaerobic workstation ensures regeneration of the highest possible bacterial activity. Material could be stored at -70°C for at least 12 months.

Characterization of Contents of Distal Ileum and Cecum to Which Drugs/Drug Products are Exposed During Bioavailability/Bioequivalence Studies in Healthy Adults.

PURPOSE: Characterize the contents of distal ileum and cecum in healthy adults under conditions simulating the bioavailability/bioequivelance studies of drug products in fasted and fed state. METHODS: Twelve males participated in a two-phase crossover study. Phase I: subjects remained fasted overnight plus 4.5 h in the morning prior to colonoscopy. Phase II: subjects remained fasted overnight, consumed breakfast in the morning, and abstain from food until colonoscopy, 4.5 h after breakfast. Upon sampling, volume, pH and buffer capacity were measured; after ultracentrifugation, supernatant was physicochemically characterized and non-liquid particles diameter was measured. RESULTS: In distal ileum, pH is ~8.1 and size of non-liquid particles is ~200 µm, regardless of dosing conditions; in fed state, liquid fraction was lower whereas osmolality and carbohydrate content were higher. In cecum, the environment was similar with previously characterized environment in the ascending colon; in fasted state, size of non-liquid particles is smaller than in distal ileum (~70 µm). Fluid composition in distal ileum is different from cecum, especially in fasted state. CONCLUSION: Differences in luminal environment between distal ileum and cecum may impact the performance of orally administered products which deliver drug during residence in lower intestine. Dosing conditions affect cecal environment more than in distal ileum.

Versican but not decorin accumulation is related to malignancy in mammographically detected high density and malignant-appearing microcalcifications in non-palpable breast carcinomas.

BACKGROUND: Mammographic density (MD) and malignant-appearing microcalcifications (MAMCs) represent the earliest mammographic findings of non-palpable breast carcinomas. Matrix proteoglycans versican and decorin are frequently over-expressed in various malignancies and are differently involved in the progression of cancer. In the present study, we have evaluated the expression of versican and decorin in non-palpable breast carcinomas and their association with high risk mammographic findings and tumor characteristics. METHODS: Three hundred and ten patients with non-palpable suspicious breast lesions, detected during screening mammography, were studied. Histological examination was carried out and the expression of decorin, versican, estrogen receptor α (ERα), progesterone receptor (PR) and c-erbB2 (HER-2/neu) was assessed by immunohistochemistry. RESULTS: Histological examination showed 83 out of 310 (26.8%) carcinomas of various subtypes. Immunohistochemistry was carried out in 62/83 carcinomas. Decorin was accumulated in breast tissues with MD and MAMCs independently of the presence of malignancy. In contrast, versican was significantly increased only in carcinomas with MAMCs (median ± SE: 42.0 ± 9.1) and MD (22.5 ± 10.1) as compared to normal breast tissue with MAMCs (14.0 ± 5.8), MD (11.0 ± 4.4) and normal breast tissue without mammographic findings (10.0 ± 2.0). Elevated levels of versican were correlated with higher tumor grade and invasiveness in carcinomas with MD and MAMCs, whereas increased amounts of decorin were associated with in situ carcinomas in MAMCs. Stromal deposition of both proteoglycans was related to higher expression of ERα and PR in tumor cells only in MAMCs. CONCLUSIONS: The specific accumulation of versican in breast tissue with high MD and MAMCs only in the presence of malignant transformation and its association with the aggressiveness of the tumor suggests its possible use as molecular marker in non-palpable breast carcinomas.